An apparatus was developed for the determination of the engine oil contribution to both total and extractable particulate exhaust emissions from diesel-powered vehicles during cyclic operation on a chassis dynamometer. For the five vehicles tested, the percentage of the total particulate material that was derived from engine oil ranged from 7 to 14%. Between 14 and 26% of the total particulate material was extractable with benzene-ethanol (80-20) solvent. Oil contributed from 30 to 55% of the extractables in most cases.Engine design and oil formulation generally appeared to have only small effects on the oil contribution to the particulate emissions. A 1982 model-year vehicle with a 1.8L engine was an exception, since its oil contribution to the total and especially to the extractable particulate emissions (14 and 95%, respectively) was significantly greater than for any of the other vehicles.